The present invention relates to a method of dispatching for manufacturing the semiconductor integrated circuit, and more specifically, to a method of determining the moves of integrated circuit devices in the FAB on a future day.
A typical process in manufacturing the semiconductor integrated circuit requires hundred of steps. These steps include several kinds of stages that are diffusion, lithography, etching, ion implantation, deposition and sputtering. In these kinds of stages, diffusion and implantation generally require longer processing time than other process stages. They need about four to twelve hours. Thus, these stages with long processing time are commonly performed on several wafer lots (commonly referred to as a xe2x80x9cbatchxe2x80x9d).
In a semiconductor""s processing line, several batches and many kinds of products are put into the processing line continuously at the same time. Thus, many kinds of products are performed on during different kinds of stages in the processing flow, but the processing time of each product is different from each other, thus wafers to be dispatched into one stage of processing flow is the dispatching problem.
For example, there are N kinds of products in a processing flow. When these products are in the etching stage of the processing flow, the equipment number of the etching stage is finite; it may be m equipment. The capacity demand problem of the stages in the processing flow exists, such the numbers of wafer lots are put into the etching stage, or the numbers of wafer lots are put into the processing flow. The problem also includes the prediction of the capacity demand forecast of the processing flow in future.
If the throughput of wafers in one stage is too much then the waiting time of the wafers in the stage is longer than the waiting time in other stages. If the number of working equipment of a stage is too small then the waiting time of the wafers is longer than the waiting time in other stages, too. Thus, the preceding stage will be a bottleneck of a processing flow. However, the manufacturing line is rarely balanced in a semiconductor""s foundry Fab, especially in its ramp-up period. The possible reasons may be changeable demand, unstable tool status, unsteady process and/or disaster events. Consequently, bottleneck tools are also varied frequently.
The traditional capacity checking system calculates the tool utilization by assuming linear loading for equipment. However, this assumption is not always true in semiconductor foundry Fab, especially in its ramp-up stage. Accordingly, the traditional method can not work well and the capacity requirement is always biased in a foundry Fab.
FIG. 1A illustrates a traditional capacity checking system. The system is the calculating method of tool capacity requirement (daily moves) assuming linear WIP coming to each tool based on planned product mix and it is a static capacity checking system. This method will lead to a biased capacity plan if WIP was not linearly distributed.
Nevertheless, in semiconductor manufacturing Fab, WIP distribution would not be linear due to the quickly changing demand, poor tool stability and low process capability, especially in its ramp-up period. Mobile bottlenecks commonly exist in such non-linear WIP dirstributed Fab. Therefore, the compatible tools between different stages and product must be allocated in order to reduce the impacts of mobile bottlenecks.
Hence, the traditional capacity checking method is a static method that cannot be suitable semiconductor manufacturing Fab. This method is useful only for a balanced manufacturing line. If this method is applied to an unbalanced manufacturing line; then it cannot calculate the variations of every stage of a process flow for daily changes.
A calculating method of the dynamic capacity demand is needed. The dynamic method considers the variation of a processing flow in every working day, and predicts the capacity demand and forecast of a processing line.
A calculating method for dynamic capacity demand forecast is disclosed. The method is applied to a processing line. There are N types of products and m types of stages in a processing line. The method calculates the work-in-process (WIP) and a turn ratio of an i-th product at a j-th stage on the k-th day, then uses these two numbers for the formula 35 of the present invention to obtain the WIP and the moves of the i-th product at the j-th stage on the k+1 day, then the WIP and the moves of every product at every stage in future are determined. Consequently the capacity demand in the future is also determined. According to these suggestions, supervisors of the processing line can vary the parameters of the processing line.